The use of wireless communication devices such as telephones, pagers, personal digital assistants, laptop computers, etc., hereinafter referred to collectively as “mobile appliances” or “mobiles stations” has become prevalent in today's society. In recent years, at the urging of public safety groups, there has been increased interest in technology which can determine the geographic position or “geo-locate” a mobile station in certain circumstances. The success of locating a mobile station depends on the availability of accurate calibration data representing the geographical region of the wireless network.
A wireless network is subject to various adjustments and changes over time. Even though some of those changes may not occur frequently, it is possible that certain components are adjusted, installed or removed on a daily basis. For example, in certain areas of the network, the peak wireless data traffic may only occur during a particular part of the day (i.e., a shopping mall between the hours of 10:00 am and 8:00 pm), and one or more components of the wireless network may be adapted during that time to handle such traffic. At other times, it may be that there is less wireless data traffic in a particular area (i.e., a shopping mall between the hours of midnight and 8:00 am), so during such times it may be more efficient to allocate those system resources elsewhere (i.e., moving the antenna coverage away from the mall during closure periods).
In general, the wireless network configuration may be considered a dynamic entity. It may be necessary to distinguish between anticipated changes that are known to the network operator and/or the location system operator, and changes that are sudden and/or unanticipated such as an immediate network related change (i.e., a particular sector change or failure etc.). A predetermined procedure may be installed to make adjustments for those anticipated changes that are known to occur on a scheduled basis, however, a different approach may be necessary for sudden or unanticipated occurrences.
When some aspect of the network changes which impairs the geo-location capability, it may be detrimental to the safety and well being of the network users. It is important that the geo-location finder system functions continuously with minimum degradation. Geo-location estimate calculations rely on accurate and updated calibration data to correctly locate a mobile station. In some instances, it may be necessary to perform re-calibration on areas of the network that have been exposed to network configuration changes.
Re-calibration efforts can often be burdensome, time consuming and expensive. Further, the network configuration may have only changed in one particular area, thus making an entire re-calibration process redundant. Modifying the previously collected calibration data to account for changes that have occurred in the network may increase the accuracy of estimating the mobile station location. Additionally, modifications to pre-existing calibration data may reduce time and costs otherwise necessary to maintain updated calibration data.
One embodiment of the present subject matter is a method to modify wireless network calibration data by comparing a first set of calibration data to a second set of data, the first set of calibration data representing measured signal power obtained at a plurality of locations in communication range of the geographical area of the wireless network, the second set of data representing prediction signal power obtained via a computational device where the prediction signal power may not be based on the values of the measured power signals. The method may further determine at least one function to represent at least one difference between the actual measured power signals and the prediction power signals, and modify one or more values of the first set of calibration data based on the at least one function.
Another embodiment of the present subject matter is a method to modify wireless network calibration data by detecting at least one of an increase and a decrease in the amount of data traffic within a coverage area of at least one base station in the wireless network and adding or subtracting at least one traffic channel to accommodate the change in data traffic. The method may further modify one or more values of the wireless network calibration data to reflect the change in the number of traffic channels by replacing the one or more values of the wireless network calibration data via prediction calibration data that is obtained via a computing device, and which is computed independent of the values of the wireless network calibration data.
Yet another embodiment of the present subject matter is a method to modify wireless network calibration data by comparing a first set of calibration data to a second set of data, the first set of calibration data representing at least the actual measured power signal levels of a signal power of a serving base station and a signal power of at least one neighboring base station, where the power signal levels were obtained at one or more location points in communication range of the geographical area of the wireless network. The second set of calibration data may represent prediction power signals obtained via a computational device where the prediction signal power may not be based on the values of the actual measured power signals. The method may further determine at least one function to represent at least one difference between the actual measured signal power and the prediction power signals and modify at least one value of the first set of calibration data based on the at least one function, where the modified at least one value includes changing the power level of the at least one neighboring base station. The method may also compare the signal power level of the serving base station to the signal power level of the modified at least one neighboring base station. If the modified neighboring base station has a higher signal power level at a particular location point than the signal power level of the serving base station at that same location point, then the method may change the status of the neighboring base station by designating the neighboring base station as a new serving base station and designating the previously recognized serving base station as a neighboring base station.
Yet still another embodiment of the present subject matter is a method to modify wireless network calibration data by determining a power level change in signals transmitted and/or received by one or more base stations communicating within a predefined region and identifying at least a portion of the predefined region that may be affected by the power level change, examining a collection of calibration data parameters to determine which data parameters represent location points within the portion of the predefined region affected by the power level change. The method may further modify the data parameters within the portion of the predefined region affected by the power level change based on the value of the power level change.
These and other advantages of the disclosed subject matter over the prior art will be readily apparent to one skilled in the art to which the disclosure pertains from a perusal of the claims, the appended drawings, and the following detailed description of the preferred embodiments.